Rapid and efficient solvent-free synthesis of 4-amino-3-mercapto-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one 1 under microwave irradiation is described. Some new fused heterobicyclic nitrogen systems such as 1,2,4-triazino[3,4-b][1,3,4]thiadiazinones, 1,3,4-thiadiazolo[2,3-c][1,2,4]triazinone and pyrazolo[5,1-c]-[1,2,4]triazine-7-carbonitrile, have been synthesized by treatment of 1 with bifunctional oxygen and halogen compounds, CS₂/KOH and malononitrile via heterocyclization reactions, in addition to some uncondensed triazines. Structures of the products have been deduced from their elemental analysis and spectral data (IR, ¹H-NMR, ¹³C-NMR). Select new synthesized compounds were screened as anticancer agents, with some showing activity as cytotoxic agents against different cancer cell lines.

[1,2,4]Triazolo[5,1‐b]‐ and [1,2,4]triazino[3,2‐b] quinazolines have been ribosylated by coupling with 1‐O‐acetyl‐2,3,5‐tri‐O‐benzoyl‐β‐D‐ribofuranose and by using the silylation method, followed by debenzoylation by methanolic sodium methoxide to afford the corresponding free N‐nucleosides. Nucleosides obtained have been identified by their spectral analysis. From the UV‐visible and fluorescence studies of some nucleosides synthesized, it is found that they have fluorescence properties.

A series of new 8-arylhydrazono-2-(benzylsulfanyl)-7H-purin-6-ones 6 were synthesized, their electronic absorption spectra in different organic solvents of varying polarities were investigated and their acid dissociation constants in both the ground and excited states were determined spectrophotometrically. The tautomeric structures of such products were elucidated by spectral analyses and correlation of their acid dissociation constants with the Hammett equation. The results indicated that the studied compounds 6 exist predominantly in the hydrazone tautomeric form 6A in both the ground and excited states.

The synthesis of various 2,4-disubstituted 4H-1,3,4-thiadiazino-[5,6-b]quinoxalines via reaction of hydrazonoyl halides with 2-amino-3-quinoxalinethiol in ethanol in the presence of sodium ethoxide is described. The structures of the reaction products were elucidated by chemical evidence and by their IR, ¹ H, ¹³ C-NMR, and MS spectra. The mechanism of the formation of the products is also discussed.

The condensation of 6-amino-2-thioxo-2,3-dihydro-1H-pyrimidine-4-one [compound (1)] with aromatic aldehydes (2) afforded azomethine derivatives (3). The formed azomethines underwent glycosidation with α-acetobromoglucose (4) to form the corresponding pyrimidine N-glycosides (6) and not S-glycosides (5). The interaction of (3) with 1-O-acetyl-2, 3, 5-tri-O-benzoyl-β-D-ribofuranose (8) afforded the corresponding pyrimidine N-riboside (10) and not S-riboside (9). Deacetylation and debenzoylation of each of (6) and (10) by using methanolic sodium methoxide afforded the corresponding free N-nucleosides (7) and (11), respectively. Next, the reaction of 2-benzylthio-6-benzylidenaminouracil (13) with (4) and (8) did not yield the corresponding protected N-nucleosides (14) and (17), whereas it afforded (15) and (18), respectively. The latter compounds (15) and (18) were stirred in methanolic sodium methoxide to yield the corresponding free N-nucleosides (16) and (19), respectively. The structures of products have been elucidated and reported and also some of the products were screened for their antimicrobial activity. Graphical